The present invention relates to a process for operating a hybrid vehicle, particularly a so-called full hybrid that can be operated in an internal-combustion-engine-driven mode and/or in an electric-motor-driven mode.
It is known that hybrid vehicles are distinguished by the combination of an internal-combustion engine and at least one electric motor. So-called full hybrids optionally permit driving by means of only the internal-combustion engine, only electric-motor driving, during which the internal-combustion engine is uncoupled or switched off, and a combined driving during which the internal-combustion engine is assisted by the at least one electric motor. Operating strategies of full-hybrid vehicles for the purpose of saving fuel change into the “electric-driving” operating mode when the driving power desired by the driver is comparatively low, the state of charge of the battery is relatively high and other basic parameters, such as the instantaneous vehicle speed, the battery temperature, etc. permit it.
Even on relatively short routes having a length of far less than 5 kilometers, purely electric driving requires more energy than today's energy accumulators can normally supply. In fairly long traffic jams or fairly long slow-driving phases, such as steadier traffic zones, the lack of energy can rapidly result in a limitation or termination of the “electric-driving” operating condition.
It is an object of the invention to indicate a process for the operation of a hybrid vehicle, wherein electric driving can take place as long as possible in phases of traffic jams and/or slow driving.
This and other objects are achieved by a process for operating a hybrid vehicle that can be operated in an internal-combustion-engine-driven mode and/or in an electric-motor-driven mode. On a route section to be traveled and considered for driving in the electric-motor-driven mode, a change to the electric-motor-driven mode will take place only when a threshold value is exceeded which represents the efficiency advantage achievable on the route section by a change from the internal-combustion-engine-driven mode to the electric-motor-driven mode. Starting from the instantaneous position of the hybrid vehicle, the route is examined in an anticipatory manner with respect to such a route section, wherein the threshold value is adapted when such a route section was recognized, and a driving through the route section in the electric driving mode would probably lead to a lowering of the state of charge of the electric energy accumulator into a critical state of charge range.
The invention recognizes that the energy saving potential existing in the electric driving operation in comparison to the driving operation using an internal-combustion engine will be the greater the lower the driving power demanded by the driver. The invention therefore consists of “distributing”, in the event of a threatened lack of stored energy, the electric energy in a manner that is as anticipatory as possible to those route sections in which the efficiency advantage of the electric-motor driving is particularly high in comparison to driving using the internal-combustion engine. In other words, in the event of an anticipated or expected lack of electric energy, the “electric driving operation window” is limited in comparison to conditions in which sufficient electric energy is present in the accumulator, which results in an improved utilization of the existing electric energy.
As a result of an anticipatory limitation of the electric driving to route sections with very low driving power, energy for the (limited) electric driving will be available for longer periods of time. The energy present in the electric energy accumulator is therefore not “wasted” at high driving powers demanded by the driver at which, although the specific consumption advantage of the electric driving exists, it is comparatively low, but this energy is preferably used in a targeted manner at lower driving powers demanded by the driver, which is advantageous with respect to energy and permits electric driving for a longer period of time.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.